Electronic earth leakage current device

ABSTRACT

An electronic earth leakage current device, comprising: 
     a moving contact and a fixed contact which can be mutually coupled/uncoupled; and 
     first sensor means for detecting an earth leakage current and for generating an electric signal which is indicative of the value of the earth leakage current; and 
     first electronic means which are electrically connected to the first sensor means in order to generate, on the basis of the electric signal which is indicative of the value of the earth leakage current, an electric tripping signal; and 
     actuation means, operatively connected to the moving contact, in order to perform, in response to an electric tripping signal, the separation of the moving contact from the fixed contact; 
     Its particularity consists of the fact that it comprises: 
     second sensor means for detecting one or more physical values which are indicative of the operating condition of the electronic device for protection against earth leakage current; and 
     second electronic means, electrically connected to the second sensor means, for receiving from the second sensor means electric signals which are indicative of the operating condition of the electronic device for protection against earth leakage current and for generating an electric tripping signal depending on the electric signals.

DESCRIPTION

The present invention relates to an electronic earth leakage currentdevice for a low-voltage power line, having improved functionality.

In particular, the present invention relates to an electronic earthleakage current device, for single- or three-phase low-voltage powerlines (therefore for voltage values below 1 KV).

Many examples of electronic earth leakage current devices for alow-voltage power line are known.

The main function of an electronic earth leakage current devices is tointerrupt the power line if an earth leakage current (or residual earthfault current or imbalance current), above a certain preset threshold,is detected. The power line, on which a tripping event occurs, can bethe power supply line (single- or three-phase) related to a specificload or to a local electrical user, for example of the industrial ordomestic type.

The expression “earth leakage current” is to be understood asdescribing, for example, an earth fault current generated by anymalfunction of the power line or of the electric loads to which thepower line is connected.

For this reason, known electronic devices generally comprise thefollowing functional elements (FIG. 1):

a current sensor 1 for detecting an earth leakage current (also known asimbalance current or residual fault current) in a phase conductor of apower line 5;

an electronic circuit 2 for processing a signal, which is indicative ofthe earth leakage current, sent by the current sensor 1.

Tripping events, which cause the interruption of the power line, occur,according to universally acknowledged technical standards, which set thetechnical requirements to be met in order to consider the electronicearth leakage current device safe for the user.

In common practice, a tripping characteristic is determined for eachelectronic earth leakage current device. This tripping characteristicdepends on the constructive characteristics of the device and ultimatelyon the characteristics of the electronic circuit 2 of FIG. 1.

It is known that the electronic earth leakage current devices of thestate of the art have drawbacks.

First of all, known electronic earth leakage current devices aregenerally not provided with monitoring systems, which allow to easilycheck the operating condition of the device and to interrupt the powerline, if necessary. This can be a source of many problems for the user.For example, a high operating temperature, caused by environmentalfactors or internal faults, can cause a malfunction of the device, whichcan compromise its safety.

The absence of monitoring of the voltage level of the power line alsocan lead to malfunctions of the device and to damage to the electricdevices powered by the power line, without having a tripping event.

The operating condition of the device in relation to its connection tothe conductors of the power line to which it is connected is also veryimportant.

If monitoring of the connection status of the conductors (neutral orground or phase) of the power line is not provided, the device may failto operate due to the interruption of one of said conductors or due totheir incorrect connection. In practice, in such situations an earthleakage current in the power line would not trip the earth leakagecurrent device. Accordingly, no protection of any kind would be providedfor a user who happened to interact in some way with the power lineand/or with the load supplied by said line. This fact entailsconsiderable safety problems, which, at present, can be solved bycoupling an electromechanical protection device to the electronic earthleakage current device, with a considerable increase in installationcosts.

Furthermore, known earth leakage current devices generally compriseelectronic circuits for setting the minimum tripping current and/or themaximum time interval for tripping. These circuits are generallyconstituted by electronic networks of the RC type, which process theelectric signal, which is indicative of the value of the earth leakagecurrent, that arrives from the current sensor. For example, the maximumtime interval is commonly set by means of introducing a time delayproportional to the detected earth leakage current value. Although thetechnical solutions that are commonly adopted allow to preset someimportant parameters that characterize the tripping criteria of theelectronic earth leakage current device, they do not allow to define inadvance its overall behavior and therefore the trend of its trippingcharacteristic. This fact entails a high degree of uncertainty as to thebehavior of the device for high earth leakage current values, for whichthe proportional delay introduced by commonly adopted technicalsolutions tends to drop to negligible values.

In this manner, there is no longer any control over the tripping timesof the electronic earth leakage current device, which substantiallydepend on the level of wear of the mechanical or electromechanicalcomponents of the electronic earth leakage current device. This fact canlead, for example, to unexpected interruptions of the power line thatare a severe annoyance for the user. Furthermore, considerable problemscan occur if an electric system includes electronic earth leakagecurrent devices in a cascade configuration (for example a device of ageneral type, connected to a network with selective-type devices). Inthis case, the uncertainty, related to the minimum tripping time, causesproblems in managing the tripping events of the whole network ofdevices. In addition to this drawback, there is the fact that, since thetripping characteristic is difficult to predetermine, many devices canfail to comply with the standards during testing and inspection. Thisfact entails, in addition to a high degree of uncertainty as to thecompliance of the earth leakage current device to the applicablestandards, many difficulties, if it is necessary to meet particularrequirements of the electrical user for which the device is intended.For example, it is difficult to determine in advance whether a devicemust be of the general or selective type or must have a more complextripping characteristic. Accordingly, complex calibration operations arenecessary, in order to achieve a tripping characteristic, whichapproximates as closely as possible the intended one.

Another drawback arises from the fact that known electronic earthleakage current devices are generally designed to use very specifictypes of actuator. In practice, the electronic circuits that generatethe tripping signal are capable of driving only a certain type ofactuator. If one decides to change the type of actuator, then the entiredevice must be redesigned in order to ensure satisfactory performance.

Another drawback arises from the fact that, in the known electronicearth leakage current devices, the design of the electronic circuits forgenerating the signal very often takes marginally into account theoperating condition of the sensor devices, suitable to detect thepresence of an earth leakage current. In particular, technical solutionsfor monitoring, with diagnostics of the ON/OFF type, the operatingcondition of the sensor means are very often all that is provided. Sincesaid sensor means have to interface with electronics designed for otherspecific purposes (the generation of a tripping signal if a certainlevel of earth leakage current is exceeded), they can find themselves innon-optimum operating conditions, negatively affecting the performanceof the entire electronic protection device.

Therefore, the aim of the present invention is to provide an electronicleakage current device for a low-voltage power line, which allowsinterrupting the power line, if an operating condition that compromisesthe correct operation of said electronic leakage current device occurs.

Within the scope of this aim, an object of the present invention is toprovide an electronic leakage current device, which allows interruptingthe power line if its operating temperature exceeds a preset threshold.

Another object of the present invention is to provide an electronicleakage current device, which allows interrupting the power line if thevoltage of the power line exceeds a preset threshold.

Another object of the present invention is to provide an electronicleakage current device, which allows interrupting the power line, if aninterruption of the neutral and/or ground conductors of the power lineoccurs or if an incorrect connection of the phase and neutral conductorsoccurs.

Another object of the present invention is to provide an electronicleakage current device, which allows to easily preset the trend of thetripping characteristic of said device.

Another object of the present invention is to provide an electronicleakage current device, which allows to use several actuation deviceswithout substantial modifications to the electronic circuits suitable togenerate the tripping signal for said actuation devices.

Another object of the present invention is to provide an electronicleakage current device, which allows to optimize the operation of thesensors suitable for detecting the earth leakage current.

Another object of the present invention is to provide an electronicleakage current device, which allows to interrupt the power line if thesensors suitable to detect an earth leakage current malfunction.

Another object of the present invention is to provide an electronicleakage current device, which is easy to manufacture and at modestcosts.

Thus, the present invention provides an electronic leakage currentdevice for a low-voltage power line, comprising:

a moving contact and a fixed contact which can be mutuallycoupled/uncoupled; and

first sensor means for detecting a leakage current and for generating anelectric signal which is indicative of the value of said earth leakagecurrent; and

first electronic means which are electrically connected to said firstsensor means in order to generate, on the basis of said electric signal,which is indicative of the value of said earth leakage current, anelectric tripping signal; and

actuation means, operatively connected to said moving contact, in orderto perform, in response to command electric signals, the separation ofsaid moving contact from said fixed contact;

The electronic leakage current device, according to the presentinvention, is characterized in that it comprises:

second sensor means for detecting one or more physical values, which areindicative of the operating condition of said electronic device forprotection against earth leakage current; and

second electronic means, electrically connected to said second sensormeans, for receiving from said second sensor means electric signals,which are indicative of the operating condition of said electronicleakage current device and for generating said electric tripping signaldepending on said electric signals.

The electronic leakage current device, according to the presentinvention, allows achieving the intended aim and objects. In fact, itensures, by virtue of the presence of the second sensor means and of thesecond electronic means, the possibility to detect abnormal operatingconditions, which might compromise the safety of the device. Inpractice, an abnormal operating condition is considered in the samemanner as an earth leakage current and produces the tripping of theelectronic leakage current device. This forces the user to intervene insafety on the power line or on the electronic device itself in order torestore normal operating conditions.

Further characteristics and advantages of the invention will becomeapparent from the detailed description of a preferred embodiment of theelectronic leakage current device, according to the present invention,illustrated only by way of non-limitative example in the accompanyingdrawings, wherein:

FIG. 1 is a block diagram of an electronic leakage current device of aknown type;

FIG. 2 is a schematic view of an electronic leakage current device,according to the invention;

FIG. 3 is a schematic view of a constructive detail of the electronicleakage current device, according to the invention;

FIG. 4 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 5 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 6 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 7 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 8 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 9 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention;

FIG. 10 is a schematic view of another constructive detail of theelectronic leakage current device, according to the invention.

The structure of an electronic leakage current device (reference 30),according to the invention is illustrated schematically with referenceto FIG. 2.

The device 30, comprises a moving contact and a fixed contact which canbe mutually coupled/uncoupled (reference 31). The separation of themoving contact from the corresponding fixed contact obviously producesthe interruption of a power line 32.

The power line 32 can be of the single-phase or three-phase type,according to the requirements of the electric user. The device 30comprises first sensor means 33 for detecting an earth leakage currentin a phase conductor of the power line 32. The sensor means 33 thereforegenerate an electric signal indicative of the value of the detectedearth leakage current.

According to a preferred embodiment, the first sensor means 33 compriseat least one current transformer provided with a primary winding whichcomprises the conductors of the power line 32. In the case of athree-phase power line, the primary winding of the current transformercan comprise the conductors of the power line 32. Accordingly, anelectric current signal flows in the secondary winding of thetransformer in response to the presence of an earth leakage current inthe phase conductor that constitutes the primary winding. This electriccurrent signal is therefore indicative of the value of the earth leakagecurrent.

The device 30, according to the invention, furthermore comprises firstelectronic means 34, electrically connected to the first sensor means33. The first electronic means 34 generate an electric tripping signaldepending on the electric signal indicative of the value of the earthleakage current (such as for example the one sent by the sensor means33). The device 30 furthermore comprises actuation means 35, operativelyconnected to the moving contact of electric contacts 31. The actuationmeans 35 produce, in response to an command electric signals 750, theseparation of the moving contact from the corresponding fixed contactand, therefore, cause the interruption of the power line 32.

The actuation means 35 can be, for example, of the electromagnetic type(solenoid).

Again with reference to FIG. 2, the device 30 comprises second sensormeans 15 for detecting one or more physical values, indicative of theoperating condition of the electronic protection device and secondelectronic means 16. The electronic means 16 are electrically connectedto the sensor means 15, in order to receive signals 17 indicative of theoperating condition of the electronic protection device. Furthermore,the second electronic means 16 generate an electric tripping signal 18,depending on the electric signals 17. Advantageously, the first andsecond electronic means 34 and 16 comprise a first circuit network 37for generating an electric tripping signal following the reception ininput of an electric current signal. The circuit network 37 preferablycomprises (FIG. 3) a first capacitive element 42, which is connected toearth. The capacitive element 42 is charged by an electric currentsignal 40 in input, so as to generate a charging voltage. A firstcomparator element 43, electrically connected to the capacitive element42, receives in input said charging voltage and generates the electrictripping signal 39, if said charging voltage exceeds a preset referencevoltage V_(R1F2).

Advantageously, furthermore, the electronic means 16 comprise (FIGS. 2and 3) a second circuit network 20 for generating an electric trippingsignal 18, following the reception in input of an electric voltagesignal 17. The electric signal 17 is indicative of the detectedoperating condition. The circuit network 20 (FIG. 4) comprises a secondcomparator element 24 for generating a first enable signal 23, if saidelectric voltage signal 17 exceeds a preset reference voltage V_(R1F2).The circuit network 20 furthermore comprises a second circuit block 25for generating an electric current signal 11 following the reception ofsaid first enable signal 23. The signal 11 is applied in input to asecond capacitive element 26 which is connected to the earth. The secondcapacitive element 26 is charged by the electric current signal 11, soas to generate a charging voltage. A third comparator element 27 iselectrically connected to the capacitive element 26. The comparatorelement 27 receives in input the charging voltage and generates anelectric tripping signal 18 if said charging voltage exceeds a presetreference voltage V_(R1F3).

With reference now to FIG. 5, the second sensor means 15 comprise atleast one sensor 151, which is arranged inside and/or outside the device30. The sensor 151 detects the operating temperature of the device 30and generates an electric signal 160, which is indicative of the valueof said detected temperature and is meant to be sent to the secondelectronic means 16. The sensor 151 can be provided, for example, byusing an appropriately configured transistor, according to one of theknown electronic design techniques.

The sensor 151 is electrically connected to a fourth comparator element161 in order to generate a second enable signal 162 if the electricsignal 160 exceeds a preset reference voltage V_(T).

The comparator element 161 is electrically connected to a first circuitblock 163 in order to generate, following the reception of the enablesignal 162, an electric current signal 40, sent in input to the firstcircuit network 37, which generates an electric tripping signal 39.

In this manner, as soon as the operating temperature of the device 30exceeds a preset threshold, the power line is interrupted. Accordingly,any condition of potential danger for the user is prevented.

With reference now to FIG. 6, the second sensor means 15 preferablycomprise a sensor 152 for detecting the voltage of a phase F of saidlow-voltage power line. The sensor 152 can, for example, be constitutedby an ordinary voltage divider. The sensor 152 generates an electricsignal 171, indicative of the value of said detected voltage. Theelectric signal 171 is to be sent to the second electronic means 15(alternatively the electric signal 171 can be used directly as thevoltage input signal 17 of FIG. 4).

The sensor 152 is electrically connected to the second circuit network20, which generates an electric tripping signal 18.

Again with reference to FIG. 6, the second sensor means 15 can comprisea sensor 153 for detecting the electrical continuity condition of theneutral conductor. The sensor 153 can advantageously comprise a circuitnetwork 156, which is connected to a phase conductor F1, to the neutralconductor N and to the second circuit network 20. The circuit network156 comprises a resistive element and diodes arranged so as to increasethe voltage of the point designated by B once the interruption of theneutral conductor in point A has occurred.

In case of interruption, the sensor 153 generates an electric voltagesignal, indicative of the electrical continuity condition of the neutralconductor, to be sent to said second electronic means 15. The sensor 153is electrically connected to the second circuit network 20, whichgenerates an electric tripping signal 18.

Likewise, the sensor means 15 comprise a sensor 154 for detecting theelectrical continuity condition of the earth conductor of the power lineand a sensor 155 for detecting the correct connection condition of thephase and neutral conductors. Like the sensor 153, the sensors 154 and155 comprise a circuit network, which may be similar, in terms ofstructure and function, to the electric network 156 and generate,respectively, signals 173 and 174.

For example, in the case of the sensor 154, the corresponding circuitnetwork is connected between a phase conductor and the ground conductorof the power line and the second circuit network 20.

In a preferred embodiment (FIG. 2), the first electronic means 34comprise first circuit means 36 for generating an electric trippingsignal after a preset minimum time interval. It is also possible toinclude second circuit means 46 for defining a minimum value of saidearth leakage current, above which an electric tripping signal is to begenerated. Also, third circuit means 45 for generating a tripping signalwithin a maximum time interval, calculated according to a substantialrelation of inverse proportionality with respect to an earth leakagecurrent higher than said minimum value, may be included.

Advantageously (FIG. 7), the first electronic means 34 comprise thecircuit network 37 for generating an electric tripping signal 39following the reception in input of an electric current signal 40, and afourth circuit block 41 for sending, following the reception of thirdand fourth enable signals (references 42 and 43), an electric currentsignal 40 in input to the circuit network 37. The circuit block 41 isalso meant to perform, following the failed reception of the enablesignals 420 and 43, a pre-discharge of said circuit network 37. This canoccur by sending in input to the circuit network 37 a current signal 40of appropriate polarity.

Advantageously, the second circuit means 46 comprise a resistivecalibration element 620 for generating (FIG. 7), by virtue of thereception of an electric current signal 62, a first reference voltage 48which is proportional to said minimum value of the earth leakagecurrent. The third circuit means 45 advantageously comprise a thirdcapacitive element 39 connected to earth and a third circuit block 50.The circuit block 50 is meant to send an electric current signal 51 tothe capacitive element 49, depending on the second reference voltage 48,so as to generate a charging voltage across the capacitive element 49 ifan earth leakage current higher than said minimum value is present. Ifan earth leakage current higher than said minimum value is not present,then the signal 51 is sent so as to discharge the capacitive element 49.Advantageously, the circuit block 50 provides, depending on the secondreference voltage 48, a first logic signal which is used as enablesignal 42.

The third circuit means 45 can furthermore comprise a fifth comparatorelement 52 which is coupled to the capacitive element 49. The comparatorelement 52 receives in input the charging voltage across the capacitiveelement 49 and generates a second logic signal, which is used as enablesignal 43, if said charging voltage exceeds a preset reference voltage(V_(R)).

Again with reference to FIG. 7, the operation of the first, second andthird circuit means comprised in the electronic protection deviceaccording to the invention is described in greater detail.

The calibration resistor 620 generates a reference voltage, depending onwhich the circuit block charges the capacitive element 49. Inparticular, if the reference voltage indicates the presence of a valueof the earth leakage current which is higher than the minimum value, theblock 50 starts the charging process so that the charging time isinversely proportional to the detected earth leakage current. Oncecharging has been completed (enable signal 43), and if a sufficientlyhigh earth leakage current is still present (enable signal 420), theblock 41 charges the capacitive element 42. In order to ensure aconstant charging time, charging occurs in a linear manner which is notproportional to the detected earth leakage current. In this manner, aminimum time interval after which the electric tripping signal 39 isgenerated is set. The described constructive solutions are particularlyadvantageous, since they allow presetting during design the entiretripping characteristic of the electronic protection device.

The maximum time interval for tripping is in fact defined by the sum ofthe charging times of the capacitive elements 49 and 42. On the otherhand, for earth leakage current values relatively higher than thenominal value, the charging time of the capacitive element 49 becomesnegligible, while the charging time of the capacitive element 42 remainsconstant. Accordingly, a minimum tripping time is set. Finally, thecalibration resistor allows determining the minimum tripping current bygenerating the reference voltage 48. The tripping characteristic of theelectronic protection device can therefore be fully defined duringdesign. Accordingly, it is possible to decide in advance the trippingcharacteristics of the electronic protection device, allowing to bettermeeting the requirements of the electrical user.

It is also very important that pre-discharge of the capacitive elements49 and 42 is performed if the conditions for generating an electrictripping signal do not occur, according to the described criteria.

This in fact allows to avoid unwanted tripping events (untimelytrippings) caused by accumulations of charge in the capacitive elements49 and 42. The presence of accumulated charge would in fact reduce thecharging times of the capacitive elements 42 and 49 and it wouldtherefore no longer be possible to ensure a preset minimum time intervalafter which tripping is to occur.

In another advantageous embodiment, the first electronic means 34comprise fourth circuit means 60 for interfacing with the first sensormeans 33. With reference to FIG. 8, the fourth circuit means 60 receivefrom said first sensor means 33 an electric signal 61 which isindicative of the value of the earth leakage current and generate anelectric current signal 62 which is indicative of the absolute value ofthe earth leakage current.

Advantageously, the circuit means 60 comprise a fifth low-impedancecircuit block 63, which is electrically connected to the first sensormeans 33 so as to ensure their linear operation. A sixth circuit block64 is furthermore comprised and is electrically connected to the circuitblock 63 in order to receive the electric signal 61, indicative of thevalue of the earth leakage current and in order to generate an electriccurrent signal 62 indicative of the absolute value of the detected earthleakage current. Preferably, the current signal 62 is sent in input tothe calibration resistor 620, so as to generate the reference voltage48.

Advantageously, a seventh filtering circuit block 65 is comprised whichis provided with means for eliminating high-intensity noise (protectiondiodes) and/or high-frequency noise (an RC network). This embodiment isparticularly advantageous, since it allows to optimize the performanceof the sensor means 33 especially if, as commonly occurs in practice,they comprise a current transformer. In this case, the secondary windingof the current transformer can operate in substantially ideal conditions(i.e. close to the short-circuit condition).

In another preferred embodiment, the first electronic means 34 comprisesixth circuit means 70 for generating an electric tripping signal ifsaid first sensor means 33 malfunction. With reference to FIG. 9, thecircuit means 70 advantageously comprise a ninth circuit block 71 formeasuring predefined physical parameters which are indicative of theoperating condition of said first sensor means. For example, if thesensor means comprise a current transformer, it is possible to measurethe equivalent resistance of the secondary winding of the transformer.If the values of said physical parameters are not within a preset range,the circuit block 71 generates a third enable signal 72 for a seventhcircuit block 73, which is electrically connected to the first circuitnetwork 37. The circuit block 73 generates, following the reception ofthe enable signal 72, an electric current signal 40 to be sent in inputto the circuit network 37, so as to generate an electric tripping signal39.

This constructive embodiment is particularly advantageous, since itallows to avoid the possibility of failure of the electronic protectiondevice to operate, for example due to possible damage suffered duringthe assembly of the sensor means 33.

Again with reference to FIG. 2, the actuation means are advantageouslyconnected to fifth circuit means 75 which are suitable to receive anelectric tripping signal (39 and/or 18) and to generate one or morecommand electric signals 750 for activating said actuation means. Thefifth circuit means 75 preferably comprise an eighth circuit block (notshown), provided with an output stage of the latch type, which has twostable operating states. The fifth circuit means 75 furthermoreadvantageously comprise one or more electronic circuits (for example anappropriately configured transistor stage) which ensure a relativelyhigh output current. In this manner, it is possible to drive actuationmeans of a different type, without substantially modifying the firstelectronic means 36.

Advantageously, the electronic protection device according to theinvention comprises (FIG. 2) third electronic means 130, which areelectrically connected to the power line 32 in order to provide a supplyvoltage V_(CC) to the first and/or second electronic means 34 and 16.

With reference to FIG. 10, the third electronic means can comprise, forexample, a rectifier stage 131 (for example a diode bridge) which isconnected to a filtering stage 132 (for example an RC network), which isin turn connected to a regulator stage 133, suitable to provide thevarious voltage levels (reference 134) used to supply the variouscomponents or for the voltage references (such as for example thereference voltages V_(R), V_(R1F1), et cetera).

In practice, it has been found that the electronic earth leakage currentdevice 30, according to the invention, fully achieves the intended aimand objects.

Furthermore, it has been ascertained that the electronic earth leakagecurrent device 30 is easy to manufacture at low cost. In particular, thefirst and/or second and/or third electronic means can be integrated in amicroelectronic semiconductor circuit, particularly in a circuit of theASIC. (Application-Specific Integrated Circuit) type or in amicrocontroller.

This allows to considerably reducing room occupation while reducingmanufacturing costs and improving operating reliability.

What is claimed is:
 1. An electronic earth leakage current device, for alow-voltage power line, comprising: a moving contact and a fixed contactwhich can be mutually coupled/uncoupled; and first sensor means fordetecting an earth leakage current and for generating an electric signalwhich is indicative of the value of said earth leakage current; andfirst electronic means which are electrically connected to said firstsensor means in order to generate, on the basis of said electric signalwhich is indicative of the value of said earth leakage current, anelectric tripping signal; and actuation means, operatively connected tosaid moving contact, in order to perform, in response to commandelectric signals, the separation of said moving contact from said fixedcontact; characterized in that it comprises: second sensor means fordetecting one or more physical values which are indicative of theoperating condition of said electronic device for protection againstearth leakage current; and second electronic means, electricallyconnected to said second sensor means, for receiving from said secondsensor means electric signals which are indicative of the operatingcondition of said electronic device for protection against earth leakagecurrent and for generating an electric tripping signal depending on saidelectric signals.
 2. An electronic earth leakage current device,according to claim 1, characterized in that said second sensor meanscomprise at least one sensor arranged inside and/or outside saidelectronic device for protection against earth leakage current fordetecting the operating temperature of said electronic earth leakagecurrent device and for generating an electric signal, indicative of thevalue of said detected temperature, for said second electronic means. 3.An electronic earth leakage current device, according to claim 1,characterized in that said second sensor means comprise at least onesensor for detecting the voltage of a phase of said low-voltage powerline and for generating an electric signal, which is indicative of thevalue of said detected voltage, to be sent to said second electronicmeans.
 4. An electronic earth leakage current device, according to claim1, characterized in that said second sensor means comprise at least onesensor for detecting the electrical continuity condition of the neutralconductor of said power line and for generating an electric signal whichis indicative of said electrical continuity condition, to be sent tosaid second electronic means.
 5. An electronic earth leakage currentdevice, according to claim 1, characterized in that said second sensormeans comprise at least one sensor for detecting the state of electricalcontinuity of the ground conductor of said power line and for generatingan electric signal which is indicative of said electrical continuitycondition, to be sent to said second electronic means.
 6. An electronicearth leakage current device, according to claim 1, characterized inthat said second sensor means comprise at least one sensor for detectingthe correct connection condition of the phase and neutral conductors ofsaid power line and for generating an electric signal which isindicative of said connection condition, to be sent to said secondelectronic means.
 7. An electronic earth leakage current device,according to claim 1, characterized in that said first and secondelectronic means comprise a first circuit network for generating anelectric tripping signal following the reception in input of an electriccurrent signal.
 8. An electronic earth leakage current device, accordingto claim 1, characterized in that said second electronic means comprisea second circuit network for generating an electric tripping signalfollowing the reception in input of an electric voltage signal.
 9. Anelectronic earth leakage current device, according to claim 1,characterized in that said first electronic means comprise: firstcircuit means for generating an electric tripping signal after a presetminimum time interval; and/or second circuit means for defining aminimum value of said earth leakage current, an electric tripping signalbeing generated for earth leakage current values higher than saidminimum value; and/or third circuit means for generating a trippingsignal within a maximum time interval, calculated according to asubstantial relation of inverse proportionality with respect to ageneric current value higher than said minimum value.
 10. An electronicearth leakage current device, according to claim 1, characterized inthat said first electronic means comprise fourth circuit means forinterfacing with said first sensor means, said fourth circuit meansreceiving from said first sensor means an electric signal indicative ofthe value of said earth leakage current and generating an electriccurrent signal of the absolute value of said earth leakage current. 11.An electronic earth leakage current device, according to claim 1,characterized in that said actuation means are electrically connected tofifth circuit means which are suitable to receive said electric trippingsignal from said first and/or second electronic means and to generateone or more command electric signals for activating said actuationmeans.
 12. An electronic earth leakage current device, according toclaim 1, characterized in that said first electronic means comprisesixth circuit means for generating an electric tripping signal if saidfirst sensor means malfunction.
 13. An electronic earth leakage currentdevice, according to claim 1, characterized in that it comprises thirdelectronic means which are electrically connected to said low-voltagepower line in order to provide a supply voltage to said first and/orsecond electronic means.
 14. An electronic earth leakage current device,according to claim 1, characterized in that said first and/or secondand/or third electronic means are at least partially integrated in oneor more microelectronic semiconductor circuits.
 15. An electronic earthleakage current device, according to claim 2, characterized in that saidsecond sensor means comprise at least one sensor for detecting thevoltage of a phase of said low-voltage power line and for generating anelectric signal, which is indicative of the value of said detectedvoltage, to be sent to said second electronic means.
 16. An electronicearth leakage current device, according to claim 2, characterized inthat said second sensor means comprise at least one sensor for detectingthe electrical continuity condition of the neutral conductor of saidpower line and for generating an electric signal which is indicative ofsaid electrical continuity condition, to be sent to said secondelectronic means.
 17. An electronic earth leakage current device,according to claim 3, characterized in that said second sensor meanscomprise at least one sensor for detecting the electrical continuitycondition of the neutral conductor of said power line and for generatingan electric signal which is indicative of said electrical continuitycondition, to be sent to said second electronic means.
 18. An electronicearth leakage current device, according to claim 2, characterized inthat said second sensor means comprise at least one sensor for detectingthe state of electrical continuity of the ground conductor of said powerline and for generating an electric signal which is indicative of saidelectrical continuity condition, to be sent to said second electronicmeans.
 19. An electronic earth leakage current device, according toclaim 3, characterized in that said second sensor means comprise atleast one sensor for detecting the state of electrical continuity of theground conductor of said power line and for generating an electricsignal which is indicative of said electrical continuity condition, tobe sent to said second electronic means.
 20. An electronic earth leakagecurrent device, according to claim 3, characterized in that said secondsensor means comprise at least one sensor for detecting the state ofelectrical continuity of the ground conductor of said power line and forgenerating an electric signal which is indicative of said electricalcontinuity condition, to be sent to said second electronic means.